When an aircraft passes through a cloud containing water particles in the supercooled liquid state, these particles cause accretion of a layer of ice on certain parts of the aircraft. To prevent such a phenomenon from occurring, a method for detecting ice which enables detection of such ice accretions is known from document FR 2 970 946. However, the detection method described in that document does not allow detecting ice crystals already formed and present in the atmosphere.
Such ice crystals do not accrete on the aircraft but bounce on it. Such already-formed ice crystals can cause engine icing phenomena leading to power losses and/or phenomena distorting the information transmitted by the speed, angle, or temperature sensors of the aircraft . . . . It is therefore essential to detect such already-formed ice crystals.